The present invention relates to regenerating and repeating (or relaying) a transmitted signal on a ring network, and more particularly to a ring line concentrator suitable for extending a communication line.
In the conventional field of regenerating and repeating a transmitted signal, there is known, for example, a paper "Local Area Network According to Token Ring Access Method" in "Bit" magazine, Vol. 16, No. 3, 1984. According to the paper, a line concentrator (this is called as active wiring concentrator (AWC) in the paper) has a single station which has the same function (i.e., regeneration of signals, transmission of frames and the like) as those terminal stations connected to the line concentrator. This station is located downstream of the last terminal station of one or more terminal stations connected to the branch cable of the line concentrator (i.e., located at the last position of the signal flow within the line concentrator). According to the analysis of the present inventors, in, the ring, configuration of the system described in the above-identified bit magazine in case where a passive wiring concentrator is connected to the AWC lobe (branch cable), or in some other cases, the signal transmission distance from the station in an AWC to the station of the immediately downstream AWC may become long so that attenuation of a signal transmitted from the former AWC becomes great, resulting in a failure of sending the signal to the station of the immediately downstream AWC. Therefore, it becomes necessary to set up or install a ring, with a limitation that the transmission distance should be determined so as to be within the total transmission distance obtained by adding together the transmission distance between adjacent AWCs and the lobe length within the AWC concerned. Thus, the above conventional system does not sufficiently consider an extension of transmission line.